The invention relates to railroad cars, especially load-carrying cars which are used in unit trains, where a number of similar cars are maintained together in coupled relation as a unit for hauling a specific material, such as coal.
In particular, the invention relates to center sill-less type hopper or gondola railroad cars, e.g. the gondola car which is shown and described in U.S. Pat. No. 3,817,189 as having a load-carrying car body which is made of aluminum (the term "aluminum," as employed herein, embracing aluminum-based alloys), rather than heavier weight steel, to radically reduce the weight of the car, so that the payload, carried by the car, can be substantially increased. The larger payload is accommodated by an enlarged gondola body which is secured between a surrounding framework, rather than atop a center sill which extends longitudinally and centrally of the car. The framework essentially consists of a pair of transversely oriented, flat shear plates and a connecting pair of parallel side sills which extend longitudinally of the car and which interact with the shear plates to transmit the push/pull forces, imposed on the car during operation, between the car coupling devices that are located adjacent the shear plates at opposing ends of the car.
It has been found that, in center sill-less car structures of this type, the coupler forces produce high stresses in the areas where the side sills join the shear plates. These stresses peak in the lower inboard corners of the side sills closest the center axis of the car and in the upper regions of the bottom portion which is welded to the side sills. Such peak stresses, which are superimposed on local geometric concentrations and discontinuities, such as the ends of the welds, are capable of causing in such areas, fatigue failures, such as cracking. The invention is directed to alleviating this problematic condition by the provision in such areas of a specially designed member which can better withstand the high peak stresses.